More importantly, apart from Henry II, it butterflies away the whole line of the Plantagenets. No Richard the Lionheart, no John Lackland. While Henry has some time ahead of him, he has to marry someone powerful in order for him to be able to claim the throne of England. Where will he look? Champagne, Toulouse, Brittany? The Capétiens also have a whole other line, since Philippe II is butterflied away (as well as Louis IX and Philippe IV). Will they still have the same drive to centralize the kingdom?
And while Henry still has Normandy, Anjou, Maine and so on, he is probably not stronger in France than the French king himself, since the latter can depend on Aquitaine. It might make it harder for him to get Brittany.